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Abstract:

A railcar bogie includes: a cross beam configured to support a carbody; a
pair of front and rear axles respectively provided on front and rear
sides of the cross beam so as to extend along a crosswise direction;
bearings respectively provided on both crosswise-direction sides of each
of the axles and configured to rotatably support the axles; bearing
accommodating portions configured to respectively accommodate the
bearings; and plate springs extending in a front-rear direction so as to
be respectively supported by both crosswise-direction end portions of the
cross beam, end portions of each of the plate springs being respectively
supported by the bearing accommodating portions. Each of the bearing
accommodating portions includes: a case portion configured to accommodate
the bearing; and supporting portions configured to support the plate
springs. The plate springs are supported by the supporting portions on a
center side of the axle in the front-rear direction.

Claims:

1. A railcar bogie comprising: a cross beam configured to support a
carbody of a railcar; a pair of front and rear axles respectively
provided on front and rear sides of the cross beam so as to extend along
a crosswise direction; bearings respectively provided on both
crosswise-direction sides of each of the axles and configured to
rotatably support the axles; bearing accommodating portions configured to
respectively accommodate the bearings; and plate springs extending in a
front-rear direction so as to be respectively supported by both
crosswise-direction end portions of the cross beam, end portions of each
of the plate springs being respectively supported by the bearing
accommodating portions, wherein: each of the bearing accommodating
portions includes a case portion configured to accommodate the bearing
and a supporting portion configured to support the plate spring; the
plate springs include coupling plates springs and non-coupling plate
springs on at least one of the coupling plate springs; each of both end
portions of each of the coupling plate springs is coupled to and
supported by the supporting portion so as to be rotatable around a
rotating axis extending in the crosswise direction; and each of both end
portions of each of the non-coupling plate springs is supported by the
coupling plate spring so as to be movable in the front-rear direction.

2. The railcar bogie according to claim 1, wherein a portion, supported
by the supporting portion, of each of the plate springs is located lower
than a portion, supported by the cross beam, of each of the plate
springs.

3. The railcar bogie according to claim 2, wherein: a
front-rear-direction center portion of each of the plate springs is
supported by the cross beam, and both front-rear-direction end portions
of each of the plate springs are respectively supported by the supporting
portions; and each of the plate springs is bent in a substantially
circular-arc shape so as to be convex upward in a side view.

4. The railcar bogie according to claim 2, wherein: a distance between
the bearing accommodating portion on the front side and the bearing
accommodating portion on the rear side changes by elastic deformation of
the coupling plate spring, the elastic deformation corresponding to a
load.

5. (canceled)

6. The railcar bogie according to claim 1, wherein: tubular portions are
respectively formed at the both end portions of each of the coupling
plate springs so as to each form a pin hole by folding and bending each
of the end portions of the coupling plate spring; each of the bearing
accommodating portions further includes a plate portion projecting from
the case portion toward the center side in the front-rear direction of
the bogie; each of the supporting portions include a pin projecting from
the plate portion in the crosswise direction; and the both end portions
of the coupling plate spring are respectively coupled to and supported by
the supporting portions such that the pins of the supporting portions are
respectively, rotatably inserted into the pin holes of the tubular
portions.

7. The railcar bogie according to claim 6, wherein: each of sleeves is
provided between the pin and the tubular portion; and the pins and the
tubular portions are made of metal, and the sleeves are made of resin.

8. (canceled)

9. The railcar bogie according to claim 1, wherein the plate springs
further include other non-coupling plate springs is provided to be spaced
apart from the coupling plate spring in a vertical direction, and end
portions of the at least one of the other non-coupling plate springs are
supported by the supporting portions so as to be movable in the
front-rear direction.

10. (canceled)

11. The railcar bogie according to claim 1, wherein an entire spring
constant of the non-coupling plate springs is larger than an entire
spring constant of the coupling plate springs.

12. The railcar bogie according to claim 1, wherein: the coupling plate
springs are made of metal; and the non-coupling plate springs include a
plate spring made of fiber-reinforced resin.

13. The railcar bogie according to claim 1, wherein: the plate springs
include a plurality of plate springs provided so as to be spaced apart
from one another in the vertical direction; each of holders is attached
to the plurality of plate springs so as to collectively position and hold
front-rear-direction center portions of the plurality of plate springs;
and the holders are respectively fixed to the both end portions of the
cross beam.

14. The railcar bogie according to claim 1, wherein: the plate springs
include a middle plate spring, an upper plate spring provided above and
spaced apart from the middle plate spring, and a lower plate spring
provided under and spaced apart from the middle plate spring; each of the
upper plate spring and the lower plate spring includes at least the
coupling plate spring; and the middle plate spring includes the
non-coupling plate spring.

15. The railcar bogie according to claim 1, wherein each of the bearing
accommodating portions includes: an axle box configured to accommodate
the bearing; an axle box receiver configured to support the axle box; and
an elastic member provided between the axle box and the axle box receiver
so as to be elastically deformable in the front-rear direction and the
crosswise direction.

16. The railcar bogie according to claim 1, wherein each of the
supporting portions is provided at a height overlapping a height range
between upper and lower ends of the case portion.

Description:

TECHNICAL FIELD

[0001] The present invention relates to a railcar bogie from which side
sills are omitted.

BACKGROUND ART

[0002] A bogie for supporting a carbody of a railcar and allowing the
railcar to run along a rail is provided under a floor of the carbody. The
bogie is supported by a primary suspension such that axle boxes each
configured to store a bearing for supporting an axle can be displaced in
a vertical direction relative to a bogie frame. Generally, the bogie
frame includes a cross beam extending in a crosswise direction and a pair
of left and right side sills respectively extending from both end
portions of the cross beam in a front-rear direction. The primary
suspension includes an axle spring constituted by a coil spring provided
between the axle box and the side sill located above the axle box (see
PTL 1).

[0003] According to the bogie as in PTL 1, the bogie frame including the
cross beam and the side sills are manufactured by, for example, welding
heavyweight steel materials one another. Therefore, problems are that the
bogie frame increases in weight, and steel material cost and assembly
cost increase. Here, proposed is the bogie in which the side sills are
omitted from the bogie frame (see PTL 2). In the bogie of PTL 2, the
bogie frame and the axle box are connected to each other by a support
mechanism member while maintaining a certain distance between the bogie
frame and the axle box. In addition, plate springs extending in the
front-rear direction are respectively attached to both end portions of
the cross beam of the bogie frame, and both end portions of each of the
plate springs are respectively inserted in spring receivers each provided
at a lower portion of the axle box.

[0007] In the bogie of PTL 2, the plate spring is supported by the axle
boxes each located at a position immediately above or immediately under
the axle. Therefore, the length of the plate spring is required to
correspond to a distance between front and rear axles. However, if the
plate spring increases in length, the spring constant becomes small. If
the carbody is large in weight, the spring constant may be inadequate. If
the plate spring is increased in thickness as a countermeasure, the
spring constant becomes large. However, this increases the weight of the
plate spring and takes away the effect of weight reduction realized by
omitting the side sills. In a case where both end portions of the plate
spring are respectively supported by the spring receivers each provided
immediately under the axle box, the distance between the plate spring and
a rail, a track, or the like (hereinafter simply referred to as "ground")
becomes short, and obstacles and the like may contact the plate spring.
Therefore, this may be inconvenient for the running of the railcar.

[0008] Here, an object of the present invention is to provide a railcar
bogie capable of realizing a preferable spring constant without
excessively increasing the thickness of the plate spring.

[0009] 2. Solution to Problem

[0010] The present invention was made in consideration of the above
circumstances, and a railcar bogie according to the present invention
includes: a cross beam configured to support a carbody of a railcar; a
pair of front and rear axles respectively provided on front and rear
sides of the cross beam so as to extend along a crosswise direction;
bearings respectively provided on both crosswise-direction sides of each
of the axles and configured to rotatably support the axles; bearing
accommodating portions configured to respectively accommodate the
bearings; and plate springs extending in a front-rear direction so as to
be respectively supported by both crosswise-direction end portions of the
cross beam, end portions of each of the plate springs being respectively
supported by the bearing accommodating portions, wherein each of the
bearing accommodating portions includes a case portion configured to
accommodate the bearing and a supporting portion configured to support
the plate spring, and each of the plate springs is supported by the
supporting portion on a center side of the axle in the front-rear
direction.

[0011] According to the above configuration, since the plate spring is
supported by the supporting portion of the bearing accommodating portion
on the center side of the axle in the front-rear direction, the length of
the plate spring can be reduced. Thus, even if the weight of the carbody
is large, a preferable spring constant can be realized without
excessively increasing the thickness of the plate spring. A position
where the plate spring is supported by the bearing accommodating portion
is shifted toward the center side of the axle in the front-rear
direction. Therefore, the distance between the plate spring and the
ground can be adjusted so as not to be too short. Thus, the running of
the railcar is not adversely affected. In addition, since the position
where the plate spring is supported by the bearing accommodating portion
is shifted toward the center side of the axle in the front-rear
direction, the plate spring can be provided at a low position, and this
can lower the position of the cross beam. Thus, the low floor of the
carbody can be realized.

Advantageous Effects of Invention

[0012] As is clear from the above explanation, the present invention can
provide a railcar bogie capable of realizing a preferable spring constant
without excessively increasing the thickness of the plate spring.

BRIEF DESCRIPTION OF DRAWINGS

[0013]FIG. 1 is a plan view of a railcar bogie according to Embodiment 1
of the present invention.

[0020]FIG. 8 is a schematic diagram for explaining elastic deformation of
a coupling plate spring shown in FIG. 2.

[0021] FIG. 9 is a rear view for explaining curve running of the railcar
bogie shown in FIG. 1.

[0022]FIG. 10 is a schematic plan view for explaining the curve running
of the railcar bogie shown in FIG. 1.

[0023] FIG. 11 is a diagram showing Modification Example 1 of a coupling
portion of the coupling plate spring shown in FIG. 5.

[0024] FIG. 12 is a diagram showing Modification Example 2 of the coupling
portion of the coupling plate spring shown in FIG. 5.

[0025]FIG. 13 is a diagram showing Modification Example 3 of the coupling
portion of the coupling plate spring shown in FIG. 5.

[0026]FIG. 14 is a diagram of the railcar bogie according to Embodiment 2
of the present invention and corresponds to FIG. 5.

[0027]FIG. 15 is a side view of the railcar bogie according to Embodiment
3 of the present invention.

DESCRIPTION OF EMBODIMENTS

[0028] Hereinafter, embodiments according to the present invention will be
explained in reference to the drawings.

Embodiment 1

[0029]FIG. 1 is a plan view of a railcar bogie 1 according to Embodiment
1 of the present invention. FIG. 2 is a side view of the railcar bogie 1
shown in FIG. 1. FIG. 3 is a cross-sectional view taken along line
III-III of FIG. 1 and shows the railcar bogie 1. As shown in FIGS. 1 to
3, the railcar bogie 1 includes a cross beam 4 extending in a crosswise
direction as a bogie frame 3 configured to support a carbody 2 but does
not include side sills respectively extending from both end portions of
the cross beam 4 in a front-rear direction. A pair of front and rear
axles 5 are respectively provided on front and rear sides of the cross
beam 4 so as to extend along the crosswise direction. Wheels 6 are
respectively fixed to both crosswise-direction sides of each of the axles
5. Bearings 7 configured to rotatably support the axles 5 are
respectively provided at both crosswise-direction end portions of each of
the axles 5 so as to be each located on an outer side of each of the
wheels 6 in the crosswise direction. The bearings 7 are respectively
accommodated in bearing accommodating portions 8. Electric motors 11 are
attached to the cross beam 4, and gear boxes 12 each of which
accommodates a reduction gear for transmitting power to the axle 5 are
respectively connected to output shafts of the electric motors 11. The
electric motor 11 and the gear box 12 are connected to each other such
that the axle 5 can be slightly displaced with respect to the cross beam
4, that is, a slight backlash is present or elasticity is present. A
braking device (not shown) configured to brake the rotation of the wheels
6 is also provided at the cross beam 4.

[0030] A plurality of plate springs 9 extending in the front-rear
direction are provided so as to be located between the cross beam 4 and
each of the bearing accommodating portions 8. Front-rear-direction center
portions of the plate springs 9 are respectively supported by both
crosswise-direction end portions of the cross beam 4, and both
front-rear-direction end portions of each of the plate springs 9 are
respectively supported by the bearing accommodating portions 8. To be
specific, the plurality of plate springs 9 have both the function of a
primary suspension and the function of conventional side sills (the
bearing accommodating portions 8 are connected to both
crosswise-direction end portions of the cross beam 4 by using only the
plate springs 9). The plate springs 9 include: a plurality of middle
plate springs 14; a plurality of upper plate springs 15 provided above
and spaced apart from the middle plate springs 14; and lower plate
springs 16 provided under and spaced apart from the middle plate springs
14.

[0031] Each of the upper plate springs 15 includes: one coupling plate
spring 25 having both front-rear-direction end portions respectively
coupled to the bearing accommodating portions 8; and one non-coupling
plate spring 23 having both front-rear-direction end portions whose
movements in the front-rear direction are not restricted. The
non-coupling plate spring 23 is stacked on an upper surface of the
coupling plate spring 25 in a surface-contact state. Each of the lower
plate springs 16 includes: one coupling plate spring 26 having both
front-rear-direction end portions respectively coupled to the bearing
accommodating portions 8; and one non-coupling plate spring 24 having
both front-rear-direction end portions whose movements in the front-rear
direction are not restricted. The non-coupling plate spring 24 is stacked
on an upper surface of the coupling plate spring 26 in a surface-contact
state. Each of the middle plate springs 14 includes three non-coupling
plate springs 20 to 22 each having both front-rear-direction end portions
whose movements in the front-rear direction are not restricted. The
non-coupling plate springs 20 to 22 are stacked on one another in a
surface-contact state. That is, the middle plate spring 14 does not
include a coupling plate spring. The entire spring constant of the
non-coupling plate springs 20 to 24 is larger than the entire spring
constant of the coupling plate springs 25 and 26. The coupling plate
springs 25 and 26 are made of metal, and the non-coupling plate springs
20 to 24 are made of fiber-reinforced resin. However, one or more or all
of the non-coupling plate springs 20 to 24 may be made of metal.

[0032] In an empty state where no passengers are on the carbody 2, each of
the plate springs 9 is bent in a substantially circular-arc shape so as
to be convex upward in a side view. To be specific, each of the plate
springs 9 is formed in a curved shape such that both front-rear-direction
end portions thereof are located lower than the front-rear-direction
center portion thereof. In addition, the entire spring constant of the
plate springs 9 is set such that even when the vehicle occupancy of the
carbody 2 is 100% and the plate springs 9 are bent, each of the plate
springs 9 maintains the bent state so as to be convex upward in a side
view. The coupling plate springs 25 and 26 couple the bearing
accommodating portion 8 on a front side and the bearing accommodating
portion 8 on a rear side, and the bearing accommodating portion 8 on the
front side and the bearing accommodating portion 8 on the rear side are
relatively movable in the front-rear direction. Therefore, the coupling
plate springs 25 and 26 located on a left side of the bogie 1 and the
coupling plate springs 25 and 26 located on a right side of the bogie 1
can elastically deform by different curvatures depending on a load.

[0033] The front-rear-direction center portions of the plate springs 9 are
respectively positioned and held by holders 30. The holders 30 are
respectively attached to holder supporting portions 10 respectively
provided at both crosswise-direction end portions of the cross beam 4.
Air springs 13 configured to serve as secondary suspensions are
respectively mounted on the holder supporting portions 10, and the
carbody 2 is mounted on the air springs 13. Partial covers 70 each
configured to cover the lower plate spring 16 are respectively provided
at the lower plate springs 16 to prevent obstacles (such as stepping
stones) from hitting the lower plate springs 16. Instead of the partial
covers 70 or in addition to the partial covers 70, entire covers 71 each
configured to entirely cover the bearing accommodating portions 8 and the
plate springs 14 to 16 from an outer side in the crosswise direction may
be provided at the bogie 1. By these entire covers 71, the above
components are protected from the obstacles, and the design of the bogie
1 can be improved.

[0034] FIG. 4 is an important portion enlarged view showing a cross
section taken along line IV-IV of FIG. 2 and shows the holder 30 and its
periphery. As shown in FIG. 4, the holder 30 positions and holds the
front-rear-direction center portions of the plurality of plate springs 9
and is fixed to the holder supporting portion 10 of the cross beam 4 by
bolts 32. The holder 30 includes: a frame portion 43 having an inverted
U-shaped cross section whose lower portion is open; bolts 45 projecting
downward from a lower end portion of the frame portion 43; spacers 33 to
35 and rubber plates 36 to 42 provided in a space surrounded by the frame
portion 43; a closing plate 44 through which the lower end portion of the
frame portion 43 is inserted and which closes a lower end opening of the
frame portion 43; and nuts 46 fixed to the bolt 45 such that the closing
plate 44 is pressed upward.

[0035] Specifically, the rubber plate 36, the spacer 33, and the rubber
plate 37 are stacked in this order from an upper side so as to be
provided between an upper wall portion of the frame portion 43 and the
upper plate spring 15. The rubber plate 38, the spacer 34, and the rubber
plate 39 are stacked in this order from the upper side so as to be
provided between the upper plate spring 15 and the middle plate spring
14. The rubber plate 40, the spacer 35, and the rubber plate 41 are
stacked in this order from the upper side so as to be provided between
the middle plate spring 14 and the lower plate spring 16. The rubber
plate 42 is provided between the lower plate spring 16 and the closing
plate 44. By fastening the nuts 46 to cause the closing plate 44 to move
upward, the front-rear-direction center portions of the plate springs 9
are compressed, sandwiched, and strongly restrained. To be specific, the
plurality of plate springs 9 are held at predetermined positions by the
holders 30, and the holders 30 and the plurality of plate springs 9
constitute a subassembly. The rubber plate 36 may be omitted.

[0036]FIG. 5 is an enlarged view of important portions of the railcar
bogie 1 shown in FIG. 2. FIG. 6 is a cross-sectional view taken along
line VI-VI of FIG. 5 and shows the bearing accommodating portion 8. As
shown in FIGS. 5 and 6, the bearing accommodating portion 8 includes: an
axle box 50 configured to accommodate the bearing 7; an axle box receiver
52 configured to support the axle box 50; and a tubular rubber block 51
that is an elastic member provided between the axle box 50 and the axle
box receiver 52 and configured to be elastically deformable in the
front-rear direction and the crosswise direction. A clearance is formed
between the axle box receiver 52 and the axle box 50 such that the axle
box receiver 52 is displaceable with respect to the axle box 50 in the
front-rear direction and the crosswise direction. The axle box receiver
52 includes: a case portion 53 configured to accommodate the axle box 50;
a pair of plate portions 54 respectively projecting from both
crosswise-direction sides of the case portion 53 toward a center side in
the front-rear direction (toward a left side in FIGS. 5 and 6) of the
bogie 1; and columnar metal pins 56 to 58 (supporting portions) each
extending between the pair of plate portions 54 so as to project from the
plate portion 54 in the crosswise direction.

[0037] The case portion 53 of the axle box receiver 52 accommodates the
axle box 50 to indirectly accommodate the bearing 7. To be specific, the
axle box 50 and the case portion 53 constitute a case member configured
to accommodate the bearing 7 of the bearing accommodating portion 8. A
crosswise-direction interval between a pair of plate portions 54 is set
to be slightly larger than a crosswise-direction width of the plate
spring 9. The pins 56 to 58 are attached to the plate portions 54 so as
to overlap one another in plan view and be vertically spaced apart from
one another. Each of the pins 56 to 58 is provided at a height
overlapping a height range H between upper and lower ends of the case
portion 53. The pins 56 to 58 may be provided such that the pins 57 and
58 overlap each other in plan view, and the pin 56 does not overlap with
the pins 57 and 58 in plan view. Depending on the requirement of design,
each of the pins 56 to 58 may be provided at a height located on an upper
or lower side of the height range H.

[0038] Tubular portions 25a are respectively formed at both
front-rear-direction end portions of the coupling plate spring 25 of the
upper plate spring 15, and each of the tubular portions 25a forms a pin
hole 25b by folding and bending downward the end portion of the coupling
plate spring 25. Tubular portions 26a are respectively formed at both
front-rear-direction end portions of the coupling plate spring 26 of the
lower plate spring 16, and each of the tubular portions 26a forms a pin
hole 26b by folding and bending downward the end portion of the coupling
plate spring 26. The upper pins 57 are respectively, rotatably inserted
in the pin holes 25b of the tubular portions 25a, and the lower pins 58
are respectively, rotatably inserted in the pin holes 26b of the tubular
portions 26a. A pair of sleeves 59 made of resin are provided each of
between the pin 57 and the tubular portion 25a and between the pin 58 and
the tubular portion 26a. Each of the sleeves 59 includes: a tube-shaped
portion 59a in which the pin 57 or 58 fits; and a flange portion 59b
projecting in a radially outer direction from a crosswise-direction outer
end portion of the tube-shaped portion 59a. The flange portions 59b are
respectively provided between the tubular portion 25a of the coupling
plate spring 25 and the plate portion 54 and between the tubular portion
26a of the coupling plate spring 26 and the plate portion 54. Thus, the
tubular portion 25a of the coupling plate spring 25 is coupled to the pin
57 so as to be rotatable around a rotating axis extending in the
crosswise direction, and the pin 57 supports the coupling plate spring
25. Moreover, the tubular portion 26a of the coupling plate spring 26 is
coupled to the pin 58 so as to be rotatable around a rotating axis
extending in the crosswise direction, and the pin 58 supports the
coupling plate spring 26.

[0039] Each of both front-rear-direction end portions of the non-coupling
plate spring 23 stacked on the coupling plate spring 25 is supported by
the coupling plate spring 25 so as to be movable in the front-rear
direction and is not coupled to the pin 57. Each of both
front-rear-direction end portions of the non-coupling plate spring 24
stacked on the coupling plate spring 26 is supported by the coupling
plate spring 26 so as to be movable in the front-rear direction and is
not coupled to the pin 58. The middle plate spring 14 is constituted by
the non-coupling plate springs 20 to 22. Each of both
front-rear-direction end portions of the non-coupling plate spring 20
that is a lowermost layer in the middle plate spring 14 that is a group
of plate springs stacked on one another is supported by the middle pin 56
so as to be movable in the front-rear direction. To be specific, none of
the plate springs 20 to 22 of the middle plate spring 14 is coupled to
the pin 56.

[0040] As shown in FIGS. 2 and 5, each of the plurality of plate springs 9
is supported by the pin 56, 57, or 58 (supporting portions) on a center
side of the axle 5 in the front-rear direction of the bogie 1. To be
specific, the length of each of the plate springs 9 in the front-rear
direction is shorter than the distance between the front and rear axles
5. Each of the pins 56 to 58 is provided at a height overlapping the
height range H between the upper and lower ends of the case portion 53 of
the bearing accommodating portion 8, and a vertical distance between the
uppermost plate spring 23 and the lowermost plate spring 26 is also
short. In plan view, the plate spring 9 is bent in a substantially
circular-arc shape so as to be convex upward. Regarding the plate spring
9, both front-rear-direction end portions each supported by the pin 56,
57, or 58 are located lower than the front-rear-direction center portion
supported by the holder 30. If a downward load applied to the
front-rear-direction center portion of the plate spring 9 increases, the
plate spring 9 elastically deforms so as to become a substantially linear
shape in plan view. With this, the distance between the front and rear
axles 5 in the front-rear direction increases. The entire thickness of
the middle plate spring 14 is larger than each of the entire thickness of
the upper plate spring 15 and the entire thickness of the lower plate
spring 16. The thickness of each of the non-coupling plate springs 20 to
24 is larger than the thickness of each of the coupling plate springs 25
and 26.

[0041] According to the configuration explained above, since the plate
spring 9 is supported by the pin 56, 57, or 58 of the bearing
accommodating portion 8 on the center side of the axle 5 in the
front-rear direction, the length of the plate spring 9 in the front-rear
direction can be reduced. Thus, even if the weight of the carbody is
large, a preferable spring constant can be realized without excessively
increasing the thickness of the plate spring 9. A position where the
plate spring 9 is supported by the bearing accommodating portion 8 is not
a position immediately below the axle 5 but a position located on the
center side of the axle 5 in the front-rear direction and on a side of
the case portion 53. Therefore, the distance between the lowermost plate
spring 26 and the ground can be adjusted so as not to be too short. Thus,
the running of the railcar is not adversely affected. For example, the
obstacles and the like do not contact the plate spring 26. In addition,
the position where the plate spring 9 is supported by the bearing
accommodating portion 8 is not a position immediately above the axle 5
but a position located on the center side of the axle 5 in the front-rear
direction and on a side of the case portion 53. Therefore, the uppermost
plate spring 23 can be provided at a low position, and this can lower the
position of the cross beam 4. Thus, the low floor of the carbody 2 can be
realized.

[0042] As shown in FIG. 7, the spring constant of the non-coupling plate
springs 20 to 22 can be changed only by causing the position of a pin 56'
relative to an axle box receiver 52' to move in the front-rear direction
from an original position A (that is the position of the pin 56 in FIG.
5) without changing the other members, the pin 56' supporting the
non-coupling plate springs 20 to 22. For example, if the position of the
pin 56 is moved to the center side in the front-rear direction of the
bogie, the length of a portion, which contributes to the elastic force,
of the middle plate spring 14 in the front-rear direction decreases.
Thus, the stiffness of the middle plate spring 14 increases, and the
spring constant suitable for the bogie in which the spring weight is
large (for example, a bogie used for a motor car) is realized. In
contrast, if the position of the pin 56' is moved to the outer side of
the bogie in the front-rear direction, the length of the portion, which
contributes to the elastic force, of the middle plate spring 14 in the
front-rear direction increases. Thus, the stiffness of the middle plate
spring 14 decreases, and the spring constant suitable for the bogie in
which the spring weight is small (for example, a bogie used for a
trail-car) is realized. Therefore, the spring constant can be adjusted
only by changing the position of the pin 56. Thus, the design efficiency
and the producibility extremely improve. The change of the position of
the pin is not limited to the pin 56 for the middle plate spring 14. The
same effect as above can be obtained by changing the position of the pin
57 for the upper plate spring 15 and/or the pin 58 for the lower plate
spring 16. However, in such case, the length of the coupling plate spring
25 or 26 in the front-rear direction needs to be changed.

[0043] As shown in FIG. 8, when a downward load applied to the
front-rear-direction center portion of each of the plate springs 25 and
26 each of which is bent so as to be convex upward in a side view
increases, each of the plate springs 25 and 26 elastically deforms such
that the curvature thereof is decreased in a side view, and the distance
between the front and rear axles 5 in the front-rear direction increases
from a normal distance L0 to a distance L1 (for example, L1-L0≦20
mm). In contrast, when the downward load applied to the
front-rear-direction center portion of the plate spring 9 decreases, the
plate spring 9 elastically deforms such that the curvature thereof is
increased in a side view, and the distance between the front and rear
axles 5 in the front-rear direction decreases from the normal distance LO
to a distance L2 (for example, L0-L2≦20 mm). As shown in FIGS. 9
and 10, when the railcar bogie 1 runs around a curve and centrifugal
force acts on the carbody 2, a wheel load of the wheel 6 on a curve inner
side (inner rail side) becomes lower than the wheel load of the wheel 6
on a curve inner side (outer rail side), and the load applied to the
plate spring 9 on the outer rail side becomes higher than the load
applied to the plate spring 9 on the inner rail side. Therefore, the
distance L1 between the axles on the outer rail side becomes larger than
the distance L2 between the axles on the inner rail side. Thus, a
self-steering function of the wheel 6 is achieved. Therefore, lateral
pressure of the wheel 6 at the time of the curve running can be reduced,
and the performance of running through a curved line improves.

[0044] Since the coupling plate springs 25 and 26 are respectively,
rotatably coupled to and supported by the pins 57 and 58, the elastic
deformation of the plate springs 9 is smoothly performed. In addition,
since the tubular portions 25a and 26a of the pins 57 and 58 are made of
metal, and the sleeves 59 are made of resin, rotation sliding resistances
of the tubular portions 25a and 26a with respect to the pins 57 and 58
can be reduced.

[0045] By providing the non-coupling plate springs 20 to 24, the entire
spring constant of the plate springs 9 can be easily adjusted without
increasing the thicknesses of the coupling plate springs 25 and 26. In
addition, each of the non-coupling plate springs 21 to 24 is stacked on
an upper surface of the plate spring 20, 21, 25, or 26 by surface
contact. Therefore, when the entire plate springs 9 bend, sliding
friction occurs among the plate springs 20 to 26 stacked by surface
contact. Thus, a moderate damping effect can be obtained.

[0046] Since the entire spring constant of the non-coupling plate springs
20 to 24 is larger than the entire spring constant of the coupling plate
springs 25 and 26, and the thickness of each of the coupling plate
springs 25 and 26 is not excessively large, the workability of the
coupling plate springs 25 and 26 is excellent, and the spring constant
can be easily adjusted by the non-coupling plate springs 20 to 24.
Further, since the coupling plate springs 25 and 26 are made of metal,
and the non-coupling plate springs 20 to 24 are made of fiber-reinforced
resin, the entire plate springs 9 can be reduced in weight while
improving the workability and the like of the coupling plate springs 25
and 26.

[0047] Since the middle plate spring 14, the upper plate spring 15, and
the lower plate spring 16 are positioned and held by the holder 30 so as
to be spaced apart from one another in the vertical direction, the holder
30 and the entire plate springs 9 constitute a modularized subassembly.
Thus, an assembly work property improves. Further, a force of sandwiching
the plate springs 9 by the holder 30 can be adjusted only by adjusting
the nuts 46, the maintenance of the plate springs 9 can be easily
performed.

[0048] As shown in FIGS. 11 to 13, each of the sleeves configured to
respectively, externally fit the pins 57 and 58 may be formed in a
special shape. With this, the adjustment of respective wheel loads in the
bogie (respective wheel loads of the same vehicle are required to fall
within a certain range) and the adjustment of the spring constant in
accordance with the aged deterioration of the plate spring can be
performed. For example, as shown in FIG. 11, the pin holes 25b and 26b of
the tubular portions 25a and 26a of the coupling plate springs 25 and 26
are increased in diameter, and sleeves 159 each including a pin hole 159a
decentered in the vertical direction are respectively inserted into the
tubular portions 25a and 26a. With this, the spring constants of the
plate springs 25 and 26 can be adjusted by adjusting the height of the
tubular portion 25a relative to the pin 57 and the height of the tubular
portion 26a relative to the pin 58. In this case, to prevent the sleeve
159 from rotating relative to the tubular portion 25a or 26a, a stopper
structure, not shown, may be provided.

[0049] As shown in FIG. 12, each of tubular portions 125a and 126a of
coupling plate springs 125 and 126 is formed in a vertical oval shape,
and oval-shaped sleeves 259 each including a pin hole 259a decentered in
the vertical direction are respectively inserted into the tubular
portions 125a and 126a. With this, the spring constants of the plate
springs 125 and 126 may be adjusted by adjusting the height of the
tubular portion 125a relative to the pin 57 and the height of the tubular
portion 126a relative to the pin 58. In this case, even if the stopper
structure is not provided, the sleeves 259 do not rotate relative to the
tubular portions 125a and 126a. As shown in FIG. 13, each of tubular
portions 225a and 226a of coupling plate springs 225 and 226 is formed in
a lateral oval shape, and oval-shaped sleeves 359 each including a pin
hole 359a decentered in the front-rear direction (left-right direction in
FIG. 13) are respectively inserted into the tubular portions 225a and
226a. With this, the spring constants of the plate springs 225 and 226
may be adjusted by adjusting the position of the tubular portion 225a
relative to the pin 57 in the front-rear direction and the position of
the tubular portion 226a relative to the pin 58 in the front-rear
direction.

Embodiment 2

[0050]FIG. 14 is a diagram of the railcar bogie according to Embodiment 2
of the present invention and corresponds to FIG. 5. The same reference
signs are used for the same components as in Embodiment 1, and
explanations thereof are omitted. As shown in FIG. 14, in the bogie of
the present embodiment, a case portion 153 of a bearing accommodating
portion 108 is divided into two parts in a side view. Specifically, the
case portion 153 includes a substantially semicircular first divided part
153A and a substantially semicircular second divided part 153B. The case
portion 153 having a substantially cylindrical shape is formed by
contacting the divided parts 153A and 153B with each other and fastening
the divided parts 153A and 153B by bolts 160. A parting line PL of the
case portion 153 is inclined at a predetermined angle θ (For
example, 10° to 30°) with respect to a vertical line VL.

[0051] A plate portion 154 projects toward the center side in the
front-rear direction of the bogie from the second divided part 153B
located on the center side in the front-rear direction. The pins 57 and
58 each extending in the crosswise direction and having a circular cross
section and a supporting plate 156 having a quadrangular cross section
are provided at the plate portion 154. A middle plate spring 114 includes
two non-coupling plate springs 20 and 21, and both end portions of the
non-coupling plate spring 20 that is the lowermost layer are respectively
supported by the supporting plates 156 in a surface-contact state so as
to be movable in the front-rear direction. An upper plate spring 115
includes the coupling plate spring 25 and a non-coupling plate spring
123, and a lower plate spring 116 includes the coupling plate spring 26
and a non-coupling plate spring 124. Each of both end portions 123a of
the non-coupling plate spring 123 is formed in a circular-arc shape so as
to extend along the tubular portion 25a, and each of both end portions
124a of the non-coupling plate spring 124 is formed in a circular-arc
shape so as to extend along the tubular portion 26a. The other components
are the same as those in Embodiment 1, so that detailed explanations
thereof are omitted.

Embodiment 3

[0052]FIG. 15 is a side view of a railcar bogie 201 according to
Embodiment 3 of the present invention. The same reference sings are used
for the same components as in Embodiment 1, and explanations thereof are
omitted. As shown in FIG. 15, in the bogie 201 of the present embodiment,
holders 230 configured to hold a plurality of plate springs 209 are
attached to each of both crosswise-direction end portions of a cross beam
204 of the bogie frame from which side sills are omitted. The plate
springs 209 include one coupling plate spring 220 and a plurality of
non-coupling plate springs 221 to 224 stacked on the coupling plate
spring 220. Each of the plate springs 220 to 224 is bent in a
substantially circular-arc shape so as to be convex upward in a side
view. Both front-rear-direction end portions of the plate springs 220 to
224 are formed in a stepwise shape such that the spring located on an
upper side is shorter in length in the front-rear direction. Both end
portions 220a of the coupling plate spring 220 are respectively coupled
to bearing accommodating portions 208. A case portion 253 of the bearing
accommodating portion 208 is divided into two parts that are an upper
part and a lower part in a side view.

[0053] Specifically, the case portion 253 includes a substantially
semicircular lower divided part 253A and a substantially semicircular
upper divided part 253B. The case portion 253 having a substantially
cylindrical shape is formed by contacting the divided parts 253A and 253B
with each other and fastening the divided parts 253A and 253B by bolts
260 and 261. A supporting plate 254 (supporting portion) projects from
the lower divided part 253A toward the center side in the front-rear
direction. Both end portions 220a of the coupling plate spring 220 are
respectively supported by the supporting plates 254. The supporting plate
254 is located on the center side of the axle 5 in the front-rear
direction and is provided at a height overlapping a height range between
upper and lower ends of the case portion 253. The upper divided part 253B
is fixed to the lower divided part 253A by the bolt 261 in a state where
each of both end portions 220a of the coupling plate spring 220 is
sandwiched between the divided parts 253A and 253B. A portion, sandwiched
between the divided parts 253A and 253B, of each of both end portions
220a of the coupling plate spring 220 is further held by externally
banding these components by a banding member 262. Since the other
components are the same as those in Embodiment 1 described above,
detailed explanations thereof are omitted.

[0054] The present invention is not limited to the above-described
embodiments, and modifications, additions, and eliminations may be made
within the spirit of the present invention. The above embodiments may be
combined arbitrarily. For example, some of components or methods in one
embodiment may be applied to the other embodiment.

INDUSTRIAL APPLICABILITY

[0055] As above, the railcar bogie according to the present invention has
an excellent effect of being able to optimize the spring constant of the
plate spring. Thus, the present invention is useful when it is widely
applied to railcars which can achieve the meaning of the effect.